A. Literature:
The open literature, which presents issues relevant to imaging systems in general, includes the following documents which are incorporated herein by reference:
B. Analog and Hybrid (Analog-Digital) Beamformer Systems:
Relevant analog and hybrid (analog-digital) phased array beamformer system art can be found in the following patents which are incorporated herein by reference.
______________________________________ U.S. Pat. No.: Title: Inventor(s): ______________________________________ 4,140,022 MULTIPLE Samuel H. Maslak TRANSDUCER ACOUSTIC IMAGING APPARATUS 4,550,607 PHASED ARRAY Samuel H. Maslak ACOUSTIC IMAGING J. Nelson Wright SYSTEM 4,699,009 DYNAMICALLY Samuel H. Maslak FOCUSED LINEAR Hugh G. Larsen PHASED ARRAY ACOUSTIC IMAGING SYSTEM 5,014,710 STEERED LINEAR Samuel H. Maslak and COLOR DOPPLER Donald J. Burch 5,165,413 IMAGING J. Nelson Wright Hugh G. Larsen Donald R. Langdon Joel S. Chaffin Grant Flash, III ______________________________________
C. Digital Beamformer Systems:
The concept of a digital receive beamformer system has been proposed in the art with respect to ultrasound systems. By way of example, the following U.S. patents, all of which are incorporated herein by reference, discuss various aspects of such systems. The patents include:
______________________________________ U.S. Pat. No.: Title: Inventor(s): ______________________________________ 4,809,184 METHOD AND Matthew O'Donnell APPARATUS FOR Mark Magrane FULLY DIGITAL BEAM FORMATION IN A PHASED ARRAY COHERENT IMAGING SYSTEM 4,839,652 METHOD AND Matthew O'Donnell APPARATUS FOR HIGH William E. Engeler SPEED DIGITAL Thomas L. Vogelsong PHASED ARRAY Steven G. Karr COHERENT IMAGING Sharbel E. Noujaim SYSTEM 4,886,069 METHOD OF, AND Matthew O'Donnell APPARATUS FOR, OBTAINING A PLURALITY OF DIFFERENT RETURN ENERGY IMAGING BEAMS RESPONSIVE TO A SINGLE EXCITATION EVENT 4,893,284 CALIBRATION OF Mark G. Magrane PHASED ARRAY ULTRASOUND PROBE 4,896,287 CORDIC COMPLEX Matthew O'Donnell MULTIPLIER William E. Engeler 4,975,885 DIGITAL INPUT STAGE Dietrich Hassler FOR AN ULTRASOUND Erhard Schmidt APPARATUS Peter Wegener 4,983,970 METHOD AND Matthew O'Donnell APPARATUS FOR William E. Engeler DIGITAL PHASED John J. Bloomer ARRAY IMAGING John T. Pedicone 5,005,419 METHOD AND Matthew O'Donnell APPARATUS FOR Kenneth B. Welles, II COHERENT IMAGING Carl R. Crawford SYSTEM Norbert J. Plec Steven G. Karr 5,111,695 DYNAMIC PHASE William E. Engeler FOCUS FOR COHERENT Matthew O'Donnell IMAGING BEAM John T. Pedicone FORMATION John J. Bloomer 5,142,649 ULTRASONIC IMAGING Matthew O'Donnell SYSTEM WITH MULTIPLE, DYNAMICALLY FOCUSED TRANSMIT BEAMS 5,230,340 ULTRASOUND Theador L. Rhyne IMAGING SYSTEM WITH IMPROVED DYNAMIC FOCUSING 5,235,982 DYNAMIC TRANSMIT Matthew O'Donnell FOCUSING OF A STEERED ULTRASONIC BEAM 5,249,578 ULTRASOUND Sidney M. Karp IMAGING SYSTEM Raymond A. Beaudin USING FINITE IMPULSE RESPONSE DIGITAL CLUTTER FILTER WITH FORWARD AND REVERSE COEFFICIENTS ______________________________________
The basic feature of a digital receive beamformer system as disclosed above can include: (1) amplification of the ultrasound signal received at each element of an array such as, for example, a linear array; (2) direct per channel analog-to-digital conversion of the ultrasound signal with an analog-to -digital sampling rate at least twice the highest frequency in the signal; (3) a digital memory to provide delays for focusing; and (4) digital summation of the focused signals from all the channels. Other processing features of a receive beamformer system can include phase rotation of a receive signal on a channel-by-channel basis to provide fine focusing, amplitude scaling (apodization) to control the beam sidelobes, and digital filtering to control the bandwidth of the signal.
This art points out the ever present desire to achieve, in an efficient manner, a reconstructed image of high quality.